[Spatiotemporal characteristics, of the heart electrical field at the period of ventricular depolarization in athletes training endurance and strength].

As a result of haemodynamic and structural changes occurring in athletes' heart under the influence of systematic physical loads, myocardial electrical activity changes that is reflected on the electric field being formed on the body surface. The heart electrical activity during ventricular depolarization at rest has been investigated in the highly skilled athletes who train to develop physical characteristics--endurance and strength by a method of electrocardiotopography. In the investigated sportsmen under uniformity of the character of the movement of positive and negative cardioelectric potential zones and localization of extrema, and general depolarization duration, the significant distinctions of: 1) amplitude of the maximum negative extremum, 2) the time of the beginning and end of the first inversion, 3) duration of the second inversion, the initial stage and the stability period between inversions, 4) the relative location of the zones of positive and negative cardiopotentials were revealed.

[Heart electric activity during ventricular repolarization of sportsmen-swimmers at physical workload].

The research of heart electrical activity of sportsmen-swimmers has been carried out using a functional test with physical activity. Standard 12-lead electrocardiograms and the cardioelectric field on the athletes' thorax surface were analyzed at rest and in every minute of a five-minute recovery period after submaximal workload. The changes of amplitude-temporal characteristics of the heart electric field on the athletes' body surface were revealed while performing physical workload. During submaximal physical workload there was no correlation between the changes: the time of achievement of maximum values of the extrema of the heart electric field and the duration of ST-T(II) and QT(II) intervals in the electrocardiogram, an amplitude of the T(II)-wave and an absolute value of the maximum positive extremum of the heart electric field.

[Models of fetal ECG recorded on the pregnant woman's abdomen].

The article presents a literature review devoted to a description of electrical potentials of the fetus heart on the pregnant woman's abdomen using the model dipole generator. The main results of the model evaluation of the influence of extracardiac factors on the fetal ECG during pregnancy and of a choice of a preferable location of electrodes on the maternal abdomen are given. The fetal ECG models for evaluating signal filtering algorithms are described.

[Sequence of depolarization of atrial myocardium of the pig (Sus scrofa domesticus)].

By the method of multichannel synchronous cardioelectropotography, sequence of depolarization of intramural atrial layers was studied in representatives of ungulate animals--pigs. In the pig atrial myocardium there is revealed a complex picture of spreading of activation fronts, connected with non-uniform anatomical structure and subendocardial (intramural) disposition of area of initial activation. The general character of sequence of depolarization of the pig atrial myocardium is comparable with carnivores (dog) and even-toed (sheep) animals.

[The dynamics of contraction and walls motion of the calf heart left ventricle].

The echocardiographic research of the left ventricular has revealed heterogeneity of thickness of the posterior wall and interventricular septum in three parallel planes in the transverse direction of the left ventricle in calves. The amplitude of systolic motion of the left ventricle posterior wall is larger than that of the interventricular septum at the level of the mitral valve, at the level of the papillary muscles, and at the apical level. The excursion of left ventricular walls in the basal level is twice as large as the mobility of ventricular walls in the apical level. During the contraction of the myocardium, the shortness of the left ventricular transversal diameter is to great extent determined by the degree of contraction of the left ventricular wall rather than of the interventricular septum. The high contractility is revealed in calves.

[Cardioelectric field on the atrial surface in pigs].

The form and distribution of extracellular cardioelectric potentials and the sequence of the excitation wave propagation on epicardium of the pig atria were studied by the method of multichannel synchronous cardioelectrotopography. The studies have shown that in pig the excitation wave breaks on epicardium of the right atrium at the base of the upper vena cava. Negative initial atrial complexes are registered in this area. Two fronts of excitation wave spread from the zone of initial epicardial activation: one--to upper segments of dorsal and ventral sides of the right atrium, the second--to inter-atrial septum. The excitation wave comes to the left atrium with a delay relative to the beginning of depolarization of the right atrium. On account of the successive movement of the front of the excitation wave from pacemaker the two-phase potentials are formed on greater part of the epicardium of the pig atria. The lower part of the auricle of the left atrium is depolarized in atrial epicardium in the last turn. The sequence of excitation wave propagation in atrial epicardium close to ravenous (dog) and ungulate (sheep) animals and man is typical for the pig, but herewith the differences in time of covering the atria with excitation do exist.

[A cardiac electric field on the body surface in rats with left ventricular hypertrophy caused by experimental renovascular hypertension].

The dynamics of potential distribution of cardiac electric field on the body surface was studied in renovascular hypertensive rats (Goldblatt type) during the ventricular activity. Three inversions of the mutual location of positive and negative areas of the cardiac electric field on the body surface were found in normotensive and hypertensive rats during the QRS-T period. Left ventricular hypertrophy of the heart in rats caused by renovascular hypertension results in changes of temporal and amplitude characteristics of the body surface potential distribution during the initial and terminal ventricular activity. The shifting trajectory of the positive and negative areas and their extremal ranges on the body surface does not change during the ventricular activity in rats with left ventricular hypertrophy of the heart as compared to the initial normotensive state.

[Architectonic of the working myocardium fibers in pig cardiac ventricles].

Architecture of the working myocardium fibers in pig cardiac ventricles was studied using the method of layer-by-layer splitting of muscle bundles. It was shown that the muscle fiber bundles in both ventricles were arranged in three directions. Three layers of fibers were distinguished as superficial, middle and deep. The fibers of the superficial layer follow a spiral course. In the apex cordis, muscle fiber bundles penetrate deep into myocardium, giving rise to the fibers of the deep layer. Middle layer in both cardiac ventricles is represented by the ring fibers, which are absent in the apex of both right and left ventricle. Fiber orientation was found to change depending on the depth of their location and was different in both ventricles. Fibers of the deep layer in the right ventricle are arranged obliquely on the free wall, while in the interventricular septum they are directed towards apico-basal cardiac axis. In the left ventricle, fibers of the deep layer are situated spirally from the apex to the base of the heart.

[The echocardiographic study of the rabbit heart left ventricle morpho-functional parameters].

Morphometric and functional parameters of the heart left ventricle in rabbits during systole and diastole were investigated by the method of echocardiography. Morphometric parameters were studied on three levels: the mitral valve, the papillary muscles and the apical level. The internal dimension of the left ventricle uniformly decreases in three parallel planes during systole, its maximal reduction being observed on the apical level. During the contraction phase, the posterior wall thickness of the left ventricular and the interventricular septum thickness increases on the basal level to a greater extent than on the apical one. During systole, the interventricular septum movement is greater than the left ventricular posterior wall motion. During the heart cycle, the form of the left ventricular cavity changes from an ellipsoid in diastole to elliptic paraboloid in systole.

[Architecture of the rat ventricular myocardium].

The working myocardium architecture was studied in heart ventricles of Wistar rats using the method of layer-by-layer dissection. Ventricle myocardium in the rat was found to be formed by three layers: superficial (subepicardial), middle and deep (subendocardial). The superficial and deep layers were present in both ventricles, while the middle one was found only in the left ventricle. The greatest variations were detected in the orientation of superficial layer muscle fibers: in the left ventricle subepicardial fibers had mainly a longitudinal arrangement, while in the right ventricle they were arranged transversely to the heart longitudinal axis. Most of the myocardial mass in the left ventricle, with the exception of the apex, was represented by a middle layer of circular fibers. In the deep layer, the fibers were oriented longitudinally, forming the trabeculae and papillary muscles.

Time correlation between initial activation of ventricular myocardium and cardiac electric potentials on body surface in dogs.

Parameters of cardioelectric field on body surface and propagation of excitation in ventricular myocardium during initial activation were studied using multichannel synchronous electrocardiotopography. It was shown that inversion of areas of negative and positive potentials of cardioelectric field on body surface at the moment of excitation propagation to the epicardium reflected changes in the main direction of excitation wavefront in ventricles.

[Reflection of distribution of the epicardial ventricular potential on the dog body surface during electrical stimulation of the myocardium]. / Otobrazhenie na poverkhnosti tulovishcha sobaki raspredeleniia potentsiala na épikarde zheludochkov pri élektricheskoi stimuliatsii miokarda.

Electrical pacing of the apex, base, and free wall of the heart right and left ventricles, as well as the left ventricle's interventricular septum revealed that localisation of the ectopic focus determined the sequence of ventricular depolarisation, the site formation, and the pathway of displacement of the areas' positive and negative potentials and their extrema on the thoracic surface. Time of the mutual movement (inversion) of positive and negative zones on the body surface was found to depend on the pacing site in the wall of ventricles.

[Effect of hypothermia on sequence of the ventricle epicardium repolarization in rabbits]. / Vliianie gipotermii na posledovatel'nost' repoliarizatsii épikarda zheludochkov krolika.

In anaesthetised rabbits at normal body temperature, the earliest ventricles' epicardial recovery occurs at the heart apex and adjacent left ventricle's surface whereas the latest one occurs at the epicardium of the right ventricle's base. A decrease in the mediastinum temperature to 32 degrees C reversed the recovery sequence. Following the cooling of the heart, the longest prolongation of the activation-recovery interval occurred at the heart apex area and the lowest one--at the right ventricle base.

[Effect of localization of the ectopic excitation site on the sequence and duration of depolarization in the ventricular epicardium in dogs]. / Vliianie lokalizatsii éktopicheskogo ochaga vozbuzhdeniia na posledovatel'nost' i dlitel'nost' protsessa depoliarizatsii epikarda zheludochkov serdtsa sobaki.

The depth of the myocardial wall ectopic focus was found to affect spatial and temporal characteristics of the depolarization process in the heart ventricular surface. Duration of the ventricular epicardial depolarization under the ectopic foci located in subendocardial and intramural layers of the myocardium was shorter than in epicardial stimulation of the ventricles. A dependence of the ectopic excitation duration on the pacing site localization in the epicardium, was revealed. The shortest duration of the depolarization occurred under electrical stimulation of the apex and ventral part of the interventricular septum, whereas the longer one--under pacing the left ventricular base.

[Time correlation of the cardiac electric field on the body surface and depolarization sequences in the pigeon heart ventricle epicardium]. / Korreliatsiia kardioélektricheskogo polia na poverkhnosti tulovishcha i posledovatel'nosti depoliarizatsii épikarda zheludochkov serdtsa u golubia.

Multifocal depolarisation of the pigeon ventricle's epicardium was revealed. A time inversion correlation was found between cardiac electrical field's positive and negative areas on the body surface and the multifocal depolarisation of the ventricle epicardium, during the period of initial ventricular activity.